1. Field of the Invention
The invention relates in general to a carrier, and more particularly to a carrier with alternately arranged leads and indented patterns.
2. Description of the Related Art
Some existing electronic devices use an anisotropic conductive film (ACF) to connect elements and main body circuits. For example, the drive chip is electrically connected to the liquid crystal display panel (LCD panel) via an anisotropic conductive film. Of which, the anisotropic conductive film is a mixture of non-conductive synthetic resin and conductive particles, wherein the central part of a conductive particle is a polymer coated with a metallic layer such as gold, nickel or tin. The anisotropic conductive film is often used in the manufacturing process of a liquid crystal display, while the technology bonding the drive chip and the LCD panel at least includes the chip on glass (COG) technology and the chip on film (COF) or Tape Automatic Bonding (TAB) technology. The COG technology directly bonds the drive chip on the panel via an anisotropic conductive film (ACF). The COF/TAB technology bonds the drive chips onto a carrier first, and has the carrier with drive chip be bonded with a glass substrate via an anisotropic conductive film afterwards.
Referring to FIG. 1A to 1B, two cross-sectional views of a conventional semiconductor structure manufactured using chip on film technology. In FIG. 1A to 1B, semiconductor structure 10 includes a substrate 11, a carrier 12, a chip 16, an underfill material 17 and an anisotropic conductive film 18. The substrate 11 includes a substrate's surface 11a, which has a number of contact pads 13. The carrier 12 includes a polyimide film (PI film) 14 and a number of leads 15, wherein the polyimide film 14 has a film's surface 14a on which these leads 15 are alternately disposed. Referring to FIG. 1C, the chip 16 disposed on the film's surface 14a has a number of gold bumps 16a, wherein these gold bumps 16a are electrically connected to one end of these leads 15 via thermal compressing of Inner Lead Bonding (ILB) technology. The underfill material 17 is used for covering the joint of the chip 16 and the carrier 12. The anisotropic conductive film 18 which connects part of the substrate's surface 11a and part of the film's surface 14a has a number of conductive particles 18a, wherein part of these conductive particles 18a are for electrically connecting the other end of these leads 15 and these contact pads 13.
In COF manufacturing process, the expansion and contraction of materials as well as the intensity of bonding are commonly encountered problems. Material expansion and contraction will result in boning deviation between the leads 15 and the contact pads 13, leading to insufficient conductive impedance due to insufficient contact area or leading to electric short-circuits due to too small a pitch between two adjacent leads. To increase the conductive impedance between the lead 15 and the contact pad 13, a conventional practice is to let W1, the width of the contact pad 13, be larger than W2, the width of the lead 15, as shown in FIG. 1B, so that the biased positioning problem caused by material expansion and contraction can be resolved. Nevertheless, the pitch between two adjacent contact pads 13 is reduced accordingly.
When the carrier 12 and the substrate 11 are hot sealed, the anisotropic conductive film 18 will be softened under high temperature and high pressure, thereby overflowing on the substrate's surface 11a as shown in FIG. 1D. Meanwhile, part of the conductive particles 18a will spread over the substrate's surface 11a and gather at the interval between two adjacent contact pads 13. Consequently, two adjacent contact pads 13 are more likely to be electrically connected resulting in electric short-circuits as shown in FIG. 1B.